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Tolerance used for Tying Slave Nodes in TIED contacts


TIED contacts help “bond” two surfaces of different mesh densities. When using the default constraint method, the projection distance of the slave node onto to the closest master segment must be zero and this is achieved by LS-DYNA by updating the slave node coordinates such that it lies on the master surface. This coordinate update is done during initialization and does alter the geometry. To avoid significant element distortion, LS-DYNA uses a built-in tolerance to discard slave nodes that are “too-far” from the master surface. In some cases, the internal tolerance could lead to slave nodes being discarded by LS-DYNA which may otherwise be required to be tied. To enable this, LS-DYNA allows a user-defined tolerance using SST as shown below.

  • Len says:

    Hi Suri —

    Do you know the tied croiterion when the OFFSET option is invoked on the TIED contact?

    Thanks, –len

  • Suri Bala says:

    Hi Len,

    They use the same criteria as with the non-OFFSET options. Just that, they are not moved in the OFFSET option if they fall within the tolerance window.

    Suri Bala

  • zyf says:

    Hi, Suri,

    When I use *contact_tied_surface_to_surface (with or without OFFSET option) for shell elements, the contact always results in artificial stress even without external loads. Is that reasonable? I expect zero energy in structure. How to resolve this?

    Thanks. zyf

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